Metallic flat gasket

ABSTRACT

Flat gasket including a gasket plate, which has at least two gasket layers arranged on each other and in which a through-opening to be sealed is formed, the gasket plate including a supporting device which increases the total material thickness of the gasket plate and is formed by several folded-over gasket layer sections. To achieve a supporting device with locally different effective height, the flat gasket is configured such that the gasket plate has a first gasket layer with a first layer area and having a first layer thickness and in which a first folded-over gasket layer section of a supporting device is formed, and the gasket plate has a second gasket layer with a second layer area and having a second layer thickness and in which a second folded-over gasket layer section of this supporting device is formed, the first and second layer thicknesses being different.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of international application number PCT/EP2013/051938, filed on Jan. 31, 2013, which claims priority to German application number 10 2012 100 919,8, filed on Feb. 3, 2012, the entire specification of both being incorporated herein by reference.

BACKGROUND OF THE INVENTION

The invention relates to a flat gasket comprising an at least substantially metallic gasket plate, which has at least two gasket layers arranged on each other and in which at least one through-opening to be sealed is formed, the gasket plate comprising at least one supporting device which increases the total material thickness of the gasket plate in areas thereof and is formed by several folded-over gasket layer sections.

The gasket plate or its layers do not have to be purely metallic, i.e., consist of sheet metal layers, but rather one or both sides of at least one or even all of the gasket layers could be provided entirely or partially with a coating which serves for so-called microsealing, reduction of sliding friction and/or protection against corrosion.

The invention relates, in particular, to a flat gasket adapted to a flange connection of an exhaust pipe of an internal combustion engine, in particular, a flat gasket which is fitted in a flange connection of an exhaust gas recirculation line, on an exhaust gas turbocharger or between an exhaust manifold and a cylinder head.

A flat gasket of the kind mentioned at the outset is disclosed in DE 102 13 900 A. This gasket is configured as a cylinder head gasket in which at least one gasket layer consists of a spring-steel sheet and has a height-elastic sealing bead which encloses a combustion chamber through-opening, but may also run along the outer edge of the gasket plate. In this known cylinder head gasket, the supporting device is configured as a so-called stopper, which is associated with and immediately adjacent to the sealing bead in order to protect the sealing bead during installation and operation of the cylinder head gasket against undesired excessive flattenings which are detrimental to a permanent sealing function of the bead. The gasket layer sections forming a stopper, which are of tongue-shaped configuration and were folded over around their respective tongue root or are of strip-shaped configuration and were folded over along a longitudinal edge of the respective gasket layer section, are all components of one and the same gasket layer, which may be the so-called functional layer provided with the sealing bead or a so-called stopper layer of the gasket plate of this cylinder head gasket.

With a flat gasket of the kind in question sealing is effected between two sealing surfaces, facing each other, of two adjacent components, in particular, between two flanges of a flange connection, which form between them a so-called sealing gap accommodating the flat gasket and are clamped against each other usually by means of assembly screws, so that the flat gasket is pressed between the component sealing surfaces. The two components or flanges can, however, also be connected to each other by means of other known connecting and clamping means and pressed against the flat gasket. The aforementioned components may, for example, be a cylinder head and an exhaust manifold adjacent thereto (in this case, the flat gasket forms an exhaust manifold gasket) but they may also be the parts of a flange connection between two sections of an exhaust gas pipe or other components which are to be tightly connected to one another and in the connecting area of which the issuing of fluid has to be prevented by the flat gasket, which is critical, above all, in the exhaust gas area of an internal combustion engine owing to the high temperatures prevailing there. Since the pressing forces acting on the installed flat gasket are usually applied only more or less at points (above all, when assembly screws are used) and the components accommodating the flat gasket between them cannot be regarded as absolutely rigid parts in any application, there are usually considerable local fluctuations in the pressing forces acting on the installed flat gasket: Without special measures, these pressing forces are greatest at and in the immediate vicinity of the assembly screws or other connecting means and decrease as the spacing from the connecting means increases, i.e., in the case of assembly screws, they are smallest halfway between two adjacent assembly screws. However, locally different component stiffnesses and locally different thermal expansions occurring during operation in the components accommodating the flat gasket between them also influence the pressing forces acting on the installed flat gasket—all this results, without special measures, in the width of the sealing gap accommodating the installed flat gasket being locally different in size, as a rule, between the components. It is, therefore, known to form the stoppers associated with height-elastic sealing beads with a height which is variable along the stopper and to counteract deformations in the component sealing surfaces accommodating a flat gasket between them by supporting elements provided on the flat gasket, which form supporting devices for the component sealing surfaces accommodating the flat gasket between them and do not have the function of a deformation limiter/stopper for a height-elastic bead.

The following problem may, however, also arise during operation with flange connections in a longer pipeline or between a heavier module such as, for example, an oil filter or a turbocharger, and a unit carrying this module, such as an internal combustion engine: Owing to shocks, vibrations or the like, but also to thermal expansions which differ with respect to location and/or time, without special measures, the topography of the sealing gap which is formed by the flange sealing surfaces facing each other and accommodates the flat gasket, undergoes change with respect to location and time, and, under certain circumstances, the flat gasket is unable to adapt to these changes in the sealing gap topography and is, therefore, unable to compensate for the changes in the sealing gap topography. This applies, above all, when, as is the case in the exhaust gas area of an internal combustion engine, the flat gasket is subjected to high operating temperatures and then no longer has any appreciable spring-elastic properties even when classic spring-steel sheets were used for one or more layers of the flat gasket, as is the case, for example, in metallic cylinder head gaskets, for the spring-steel properties in classic spring steels are already drastically reduced at approximately 400° C. Without special measures, the flange connections can then become untight under the described operating conditions.

The object underlying the invention was to propose flat gaskets of the kind defined at the outset, with which supporting devices of locally different effective height can be simply and cost-effectively achieved. In this case, a supporting device can be a stopper associated with a sealing bead, i.e., a deformation limiter for the sealing bead, a device for delimiting or minimizing deformations of the sealing surfaces of components such as flanges between which the flat gasket is clamped, but also a supporting device by means of which the topography of the sealing gap accommodating the flat gasket is at least substantially stabilized.

SUMMARY OF THE INVENTION

To accomplish this object, it is proposed, in accordance with the invention, to so configure a flat gasket of the kind defined at the outset that the gasket plate has at least one first gasket layer with at least one first layer area in which the first gasket layer has a first layer thickness and in which at least one first folded-over gasket layer section of a supporting device is formed, and that the gasket plate has at least one second gasket layer with at least one second layer area in which the second gasket layer has a second layer thickness and in which at least one second folded-over gasket layer section of this supporting device is formed, the first and second layer thicknesses being different from each other and this supporting device, therefore, having different total material thicknesses and, consequently, different effective heights in areas thereof.

It is easiest to use flat materials of different thickness for the first and second gasket layers (i.e., uncoated sheet metals, sheet metals coated on one side or sheet metals coated on both sides in any combination), as gasket layer sections of different thickness and, consequently, different effective height then result automatically because the gasket layer sections formed by the one gasket layer have a different layer thickness than the gasket layer sections formed by the other gasket layer, but embodiments are preferred in which the first and second gasket layers comprise sheet metal layers of sheet metals of different sheet thickness.

In accordance with the invention, the flat gasket can, however, also be so configured that one or both of the gasket layers is or are provided with coatings of different thickness in areas thereof or the gasket layer sections or some of the gasket layer sections were subjected to a stamping operation for changing the sheet metal thickness in areas thereof, which, in view of the relatively small surface area of such a gasket layer section, is possible with considerably lower stamping forces than the stamping of a height profile in a stopper which is not interrupted in its longitudinal direction.

DE 102 13 900 A does mention that a stopper associated with a sealing bead can have a height profile along the bead, which is to be achieved by the stopper being formed by folded-over gasket layer sections having different heights, so that the stopper height varies in the longitudinal direction of the bead. However, how these different heights are to be achieved is not described, and since in this known cylinder head gasket all of the folded-over gasket layer sections forming a stopper are produced from one and the same gasket layer and, therefore, initially must all have the same original layer thickness, it is assumed that the different heights are created by stamping the folded-over gasket layer sections or gasket layer sections to be folded over.

If the gasket plate has a gasket layer with a, possibly height-elastic, bead, a supporting device in accordance with the invention can be associated with and adjacent to this bead (in a plan view of the gasket plate) in order to protect the bead from an undesired high degree of flattening during installation and operation of the flat gasket. The bead can be a common sealing bead, which runs around a fluid through-opening (e.g. a combustion chamber opening, an exhaust gas through-opening or a through-opening for coolant or engine oil) but, for example, also a bead enclosing a screw hole for the passage of an assembly screw. In the case of a sealing bead enclosing a fluid through-opening, a supporting device in accordance with the invention can be advantageously arranged radially outside of the sealing bead, either to form a stopper immediately adjacent to the sealing bead or to form a so-called hinterland support—in this case, the supporting device is arranged at a distinct spacing from the sealing bead, more specifically, in such a way and in such a configuration that it stabilizes the sealing gap topography during operation and/or counteracts the deformation of the sealing surfaces of components accommodating the flat gasket between them, for example, the deformation of the flanges of a flange connection lying in the exhaust gas area of an internal combustion engine. A hinterland support is typically arranged at the periphery of the gasket plate, where several supporting devices in accordance with the invention may be provided, for example, in the area of the two longitudinal ends of an elongate flat gasket. However, depending on the kind of use and configuration of the flat gasket, the supporting device can, in this case, also act as stopper for the sealing bead.

The folded-over gasket layer sections of one of the gasket layers could all be folded over onto the latter and lie against this gasket layer, and the latter could be arranged inside a multilayered gasket plate, as shown in the drawings of DE 102 13 900 A. However, the folded-over gasket layer sections of one of the gasket layers could also lie on another gasket layer and/or be located on an outer side of the gasket plate. It is, in particular, possible to provide the gasket layer sections, which are to be folded over, of one of the gasket layers at the periphery of the gasket plate and to then fold them over in such a way that they engage over the outer edge of an adjacent gasket layer and rest on the latter. Alternatively, at least one of the gasket layer sections, which are to be folded over, of a gasket layer can be arranged at a spacing from the periphery of the gasket plate and pass through a cutout in an adjacent gasket layer and be folded over onto the latter.

If the gasket layer sections of a supporting device in accordance with the invention lie on a first outer side of the gasket plate and are formed by a gasket layer which forms the second outer side of the gasket plate and the folded-over gasket layer sections of which engage over the first outer side of the gasket plate, the folded-over gasket layer sections can also ensure that the multilayered gasket plate is held together and additional measures for connecting the gasket layers to one another can, therefore, be dispensed with.

As in the cylinder head gasket disclosed in DE 102 13 900 A, in a flat gasket in accordance with the invention it is also possible for at least some of the gasket layer sections to be of strip-shaped configuration and folded over at a longitudinal edge of the respective gasket layer section. However, for formation of a supporting device having a height profile, embodiments are preferred in which at least some of the gasket layer sections are of tongue-shaped configuration and folded over around the respective tongue root—the gasket layer sections can then be of relatively narrow configuration in the longitudinal direction of the supporting device so that with them a height profile is achieved, the height of which changes at relatively short intervals in the longitudinal direction of the supporting device.

If a supporting device in accordance with the invention is desired, the height profile of which has not only two different effective heights, this can be brought about by some of the folded-over gasket layer sections being made to undergo a possibly only partial stamping operation before or after the folding-over, but in the case of a gasket plate having more than two gasket layers, it is simpler to produce more than two gasket layers from layers of different thickness and to form the supporting device from folded-over gasket layer sections of more than two gasket layers. Further alternatives will be described hereinbelow.

In preferred embodiments of the flat gasket in accordance with the invention, at least one supporting device—in a plan view of the gasket plate—is of elongate configuration (i.e. it has a general shape with a larger length than width) and is formed by at least two folded-over gasket layer sections lying one behind the other in the longitudinal direction of the supporting device (which is not necessarily to be equated with immediately following each other), the total material thicknesses of the gasket plate in the areas of at least two gasket layer sections being different from each other. Accordingly, such a supporting device has a height profile extending in the longitudinal direction thereof, which owing to its formation by folded-over gasket layer sections need not be a height profile with a continuous course and a constant change in the profile height. As is clear from the above, the easiest way to achieve such a height profile is for the layer thicknesses of at least two gasket layer sections to be different from each other.

In preferred embodiments of the flat gasket in accordance with the invention, a supporting device is formed by at least two first folded-over gasket layer sections provided in the longitudinal end areas of the supporting device and at least one second folded-over gasket layer section provided in a central area of the supporting device, the total material thicknesses of the gasket plate in the areas of the first gasket layer sections and in the area of the second gasket layer section being different from one another. Such a supporting device may, for example, in its longitudinal end areas have a larger or a smaller effective height than in its central area.

As mentioned above, with the use of connecting means provided only locally such as, for example, assembly screws, pressing forces applied only more or less at points result, without special measures, in a sealing gap accommodating the flat gasket, the width of which is smallest in the area of the connecting means and largest in central areas lying between the connecting means. Therefore, especially such embodiments of the flat gasket in accordance with the invention are recommended, in which an elongate supporting device extends between the positions of two connecting means, in particular, between two screw holes for the passage of assembly screws, and the total material thickness of the supporting device in areas near the connecting means is less than in a central area of the supporting device lying between these areas.

The basic principle of the invention can also be advantageously achieved by the gasket plate comprising at least one thicker and one thinner gasket layer, and the supporting device comprising at least two gasket layer sections of the thicker gasket layer, a first gasket layer section of which is folded over onto the thicker gasket layer and a second gasket layer section of which is folded over onto the thinner gasket layer. In this case, the effective height of the supporting device in the area of the first folded-over gasket layer section is equal to the thickness of the thicker gasket layer less the thickness of the thinner gasket layer, and in the area of the second folded-over gasket layer section equal to the thickness of the thicker gasket layer. In such an embodiment, the thinner gasket layer can extend only as far as the free edge of the first folded-over gasket layer section or as far as the free edges of the folded-over first gasket layer sections, but embodiments are preferred, in which the thinner gasket layer has a recess which—in a plan view of the gasket plate—accommodates the folded-over first gasket layer section at least substantially, and so the total material thickness formed by the thicker and thinner gasket layers in the area of the folded-over second gasket layer section is larger by the layer thickness of the thinner gasket layer than in the area of the folded-over first gasket layer section. If, in such a case, in a multilayered gasket plate, only the thicker gasket layer has folded-over gasket layer sections, a supporting device with two different effective heights can nevertheless be achieved. If, on the other hand, two gasket layers of different thickness have folded-over gasket layer sections, even a supporting device with three different effective heights can be achieved.

Furthermore, an increase in the effective heights of a supporting device in accordance with the invention can be achieved by at least one gasket layer in the area of at least one gasket layer section being folded over not only once, i.e., through approximately 180°, but by the gasket layer section itself being folded over in areas thereof once more or several times, so that the gasket layer section has in cross section the shape of a flat lying U or, for example, the shape of a flat S, which, above all, can be readily achieved on a relatively thin gasket layer.

In particularly preferred embodiments of flat gaskets in accordance with the invention, the gasket layers extend with folded-over gasket layer sections at least substantially over the entire gasket plate.

Further features, advantages and details of the invention are given in the appended drawings and/or the following description of several particularly advantageous embodiments of the flat gasket in accordance with the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a plan view of a first embodiment of a flat gasket in accordance with the invention;

FIGS. 2 to 5 show sections through this first embodiment in accordance with lines 2-2, 3-3, 4-4 and 5-5, respectively, in FIG. 1;

FIG. 6 shows a section through a second embodiment in which the folded-over gasket layer sections are to be spaced from the periphery of the gasket plate;

FIGS. 7A to 7E show sections through five further embodiments of the flat gasket in accordance with the invention, wherein each of these sectional representations shows only folded-over gasket layer sections of one, in each case, of the gasket layers of the respective flat gasket, which can be combined with one another;

FIG. 8A shows an area of an eighth embodiment of the flat gasket in accordance with the invention in a sectional isometric representation;

FIG. 8B shows a section of another area of this eighth embodiment;

FIG. 8C shows a ninth embodiment, modified in relation to FIG. 8A, of an area of a flat gasket in accordance with the invention in an isometric representation; and

FIG. 9 shows a section corresponding to FIG. 5 through a tenth embodiment of the flat gasket in accordance with the invention.

DETAILED DESCRIPTION OF THE INVENTION

The flat gasket in accordance with the invention, shown in FIGS. 1 to 5, is a particularly preferred embodiment, namely a flat gasket for a flange connection in the exhaust gas area of an internal combustion engine, which is to be installed between two flanges of the flange connection shown only in FIG. 5 and clamped, in particular, by assembly screws. The flat gasket has a gasket plate 10 with an exhaust gas through-opening 12 and—in this case—two screw holes 14 for the passage of assembly screws and consists of an, in accordance with FIG. 1, upper, thicker first gasket layer 16 and of a lower, thinner second gasket layer 18, which were produced from steel sheets, which do not scale at operating temperatures of the gasket (such steel sheets are known to one skilled in the art and, therefore, need not be specifically described). If a flat gasket in accordance with the invention is subjected during operation to less high temperatures than a flat gasket used in the exhaust gas area of an internal combustion engine, for example, an exhaust manifold gasket or a flange gasket on an exhaust gas turbocharger, the so-called functional layers of a flat gasket in accordance with the invention can be produced from spring-steel sheet metal, for which common spring steels are used. For a functional layer or the functional layers of a flat gasket in accordance with the invention which is to be installed in the exhaust gas area, known high-alloy spring steels, in particular, those made of a nickel-based alloy, are suitable as such spring steels still have spring-elastic properties at high operating temperatures. In this connection, it is pointed out that a functional layer of a metallic flat gasket is to be understood as a gasket layer having in the installed state and during operation of the gasket at least one height-elastic bead, in particular, such a sealing bead.

In accordance with the invention, the two gasket layers 16, 18 are, in the present case, substantially congruent, and each gasket layer has a sealing bead 16 a and 18 a, respectively, stamped in the sheet metal, which, in a plan view of the gasket plate 10, lie one on top of the other and enclose the exhaust gas through-opening 12 in the shape of a circular ring. In the embodiment shown, the two sealing beads 16 a, 18 a are so-called full beads of approximately circular arc-shaped or trapezoidal cross section, however, the sealing beads could also have any other cross-sectional shape known to one skilled in the art from the prior art, for example, these could be so-called half-beads. Also preferred is a configuration of the gasket such that each gasket layer 16, 18 has a flat section between its sealing bead 16 a, 18 a and the edge of the exhaust gas through-opening 12, with these flat sections also lying against each other like those areas of the two gasket layers 16, 18 lying radially outside of the sealing beads 16 a, 18 a when the gasket is installed and pressed. Differently from shown in FIGS. 2 to 4 and described hereinabove, the two gasket layers can also be provided with beads which do not face away from each other with their projections, but project towards the respective other gasket layer. Lastly, attention is drawn to the following: If a bead of a gasket layer does not have any or any appreciable elastic properties during operation but is at least substantially plastically deformed and flattened during installation and/or operation of the flat gasket, the bead in the area of its crest nevertheless results in an increased pressure in the direction perpendicular to the plane of the gasket plate and, consequently, can fulfill a sealing function, above all, when owing to an inventive configuration of the flat gasket, the sealing gap topography is stabilized by the flat gasket during operation.

The gasket plate 10 is provided with two supporting devices 20 and 22 in accordance with the invention, each of which has an elongate basic shape, in the preferred embodiment shown, is arranged at the periphery of the gasket plate 10, extends, in each case, over the major part of an essentially elongate gasket plate area lying radially outside of the sealing beads 16 a, 18 a and, in the illustrated case, lies between the two screw holes 14, and each of which consists of several segments, in the illustrated case, of four segments, which are formed by folded-over gasket layer sections of the two gasket layers 16, 18. Only the supporting device 22 is explained in detail hereinbelow, but the same applies to the other supporting device 20.

The segments, shown in FIG. 1, of the supporting device 22 are formed by folded-over first and second gasket layer sections 181 and 161, respectively, which are sections of the gasket layer 18 and the gasket layer 16, respectively, which are of tongue-shaped or strip-shaped configuration and are bent through 180°. As is evident from FIGS. 3 and 4, the thicker gasket layer sections 161 are folded over onto the gasket layer 16 itself, whereas the thinner gasket layer sections 181 engage around the edge of the gasket layer 16 and are folded over onto the gasket layer 16.

The two gasket layers 16 and 18 of the gasket plate 10 are held together by the folded-over gasket layer sections 181 and so no further connecting means are required.

Each of the two supporting devices 20 and 22 has two end areas, each of which, in the illustrated case, is adjacent to one of the screw holes 14 and is formed by a thinner, folded-over gasket layer section 181, and a central area which is formed by two thicker gasket layer sections 161, and so each supporting device has a height profile which in the two end areas of the supporting device has a lower height than in its central area.

In accordance with the invention, the two supporting devices 20, 22 can fulfill two functions:

Primarily, the two flanges 30 and 40 of the flange connection (see FIG. 5) between which the flat gasket in accordance with the invention is to be installed and clamped, are supported by the two supporting devices, and the topography of the sealing gap defined by the two flanges and accommodating the flat gasket is thereby stabilized during operation. Furthermore, the two supporting devices 20, 22 can prevent the sealing beads 16 a, 18 a, from being flattened to too great an extent in an undesired manner during installation and operation of the flat gasket, i.e., the supporting devices can also act as stoppers for the two sealing beads.

In accordance with the invention, the total material thickness of the gasket plate 10 in the areas of the folded-over gasket layer sections 161, 181 is larger than outside of the areas of the folded-over gasket layer sections or the supporting devices 20 and 22 by the material thickness of the gasket layer 16 or by the material thickness of the gasket layer 18, respectively. The effective heights of the supporting device are, therefore, equal to the material thickness of the gasket layer 16 or the gasket layer 18, respectively, and less than the sum of the heights of the undeformed sealing beads 16 a and 18 a.

The section shown in FIG. 5 indicates the gasket plate 10 only as a whole and shows the folded-over gasket layer sections 181, 161 only schematically and exaggerated in height in order to clearly illustrate the height profile of the supporting device 22. FIG. 5 also shows partial areas of two flanges 30 and 40 of a flange connection between which the flat gasket in accordance with the invention is installed and clamped by connecting means, not shown, of the two flanges. Therefore, the topography of the sealing gap which is formed and defined by the sealing surfaces, facing each other, of the two flanges 30 and 40 and in which the flat gasket in accordance with the invention is installed and clamped can be seen from FIG. 5. The size of the curvature of the flange 30 is also exaggerated in FIG. 5, and so the local differences in the height or width of the sealing gap are also exaggerated in size in the illustration in FIG. 5. It can also be taken from FIG. 5 that it may be recommendable to change the gasket layer sections, for example, the gasket layer sections 181 and 161, before or after the folding-over, in accordance with the invention, in areas thereof in their thickness by stamping operations (in relation to the cross-sectional shape shown in FIG. 5) in such a way that the folded-over gasket layer sections have a height profile adapted to the sealing gap topography, i.e., are adapted to the curvature of the flange sealing surface lying against the folded-over gasket layer sections.

Some alternative configurations of flat gaskets in accordance with the invention will now be explained with reference to FIGS. 6 and 7A to 7E, 8A to 8C and 9.

FIG. 6 shows a section through an area of a flat gasket in accordance with the invention, which is spaced from outer and inner edges of the gasket plate of this flat gasket. The gasket plate of this flat gasket is formed, only by way of example, by two gasket layers, namely a thicker upper gasket layer 50 and a thinner lower gasket layer 52. Several gasket layer sections 50 a, only one gasket layer section of which is shown in FIG. 6, were formed from the gasket layer 50 by punching and folding-over. These gasket layer sections were folded over onto the gasket layer 50 itself and placed against its upper side. Several gasket layer sections 52 a, likewise only one gasket layer section 52 a of which is shown in FIG. 6, were likewise formed from the gasket layer 52 by punching and folding-over. In order that the gasket layer sections 52 a can likewise be folded over and placed on the upper side of the gasket layer 50, the gasket layer 50 has for each folded-over gasket layer section 52 a a window-like recess 50 b through which the gasket layer section 52 a, which is first raised, can be passed and then folded back onto the gasket layer 50. For the sake of completeness, it is pointed out that the formation of the folded-over gasket layer section 50 a shown in FIG. 6 does, of course, leave a corresponding recess in the gasket layer 50.

FIGS. 7A to 7E show configurations of supporting devices in accordance with the invention, which can be provided at the outer edge and/or an inner edge of the gasket plate of a flat gasket in accordance with the invention, the arrangement at an inner edge, of course, requiring less restricted space conditions than in the case of the flat gasket shown in FIG. 1.

FIG. 7A shows an area of a three-layered gasket plate with three gasket layers 60, 62 and 64, all three of which have different material thicknesses (which, for the sake simplicity, was not shown in FIGS. 7A to 7C). At first locations on the gasket pate, gasket layer sections 64a of the lowermost gasket layer 64 form first segments of a supporting device in accordance with the invention. FIG. 7A shows only one of the folded-over gasket layer sections 64 a, but all of these were folded over onto the upper side of the uppermost gasket layer 60, thereby engaging around the edge of the gasket plate shown in FIG. 7A. At other, second locations on the gasket plate, its uppermost gasket layer 60 has gasket layer sections 60 a, which were all folded over onto the upper side of the gasket layer 60, and only one of which is shown in FIG. 7B. The folded-over gasket layer sections 60 a are to form second segments of the supporting device in accordance with the invention. At yet other, third locations on the gasket plate, this supporting device has three segments, formed by folded-over gasket layer sections 62 a of the central gasket layer 62. FIG. 7C again shows only one of these folded-over gasket layer sections 62 a, but which were all folded over onto the upper side of this gasket layer, thereby engaging around the edge of the gasket layer 60.

This supporting device in accordance with the invention, only individual segments of which are shown in FIGS. 7A to 7C, therefore has a height profile with three different effective heights.

FIGS. 7D and 7E show two further variants of a segment, in each case, of a supporting device in accordance with the invention, which is arranged in the vicinity of a bead of a flat gasket in accordance with the invention. Each of FIGS. 7D and 7E shows two gasket layers (which are meant to have different material thicknesses, but which was not shown in the drawings) of a gasket plate having two or more gasket layers. FIGS. 7D and 7E show only one bead in one of the gasket layers, but at least a second gasket layer could also be provided with a bead. Lastly, FIGS. 7D and 7E each show only a single folded-over gasket layer section of one of the gasket layers, but it is, of course, self-evident that another gasket layer of different material thickness also has folded-over gasket layer sections.

Of the two gasket layers 70 and 72 of the gasket plate shown partially in FIG. 7D, the gasket layer 72 is provided with a bead 74 and also has folded-over gasket layer sections 72 a, which were folded over onto that side of the gasket layer 72 above which the bead 74 projects. The folded-over gasket layer sections 72 a therefore form first segments of a supporting device in accordance with the invention, which can have a stopper function for the bead 74.

FIG. 7E is to illustrate another location on the same gasket plate which is formed by the gasket layers 70 and 72 and on which the gasket layer 70 has a folded-over gasket layer section 70 a. The same applies for this as for the folded-over gasket layer section 72 a, apart from the fact that the material thicknesses of the gasket layers 70 and 72 and, therefore, of the folded-over gasket layer sections 70 and 72 a are to be different.

In FIGS. 8A and 8B two areas of one and the same flat gasket in accordance with the invention are shown, the gasket plate of which can have only two or more gasket layers. FIGS. 8A and 8B show a thicker gasket layer 80 and a thinner gasket layer 82, of which only the thicker gasket layer 80 can be provided with folded-over gasket layer sections. In the area shown in FIG. 8A, the gasket layer 80 has a folded-over gasket layer section 80 a which is folded back onto the actual gasket layer 80, however, in the longitudinal direction of the bending line resulting from the folding-over of the gasket layer section 80 a, the gasket layer 80 can have at least one further folded-over gasket layer section 80 a, these folded-over gasket layer sections being arranged at a spacing from each other in the longitudinal direction of the bending line. In the embodiment shown, a right edge, in accordance with the Figure of the drawings, of the thinner gasket layer 82 runs in the vicinity of the left edge, in accordance with the Figure of the drawings, i.e., the free edge of the folded-over gasket layer section 80 a or all of the gasket layer sections 80 a. As FIG. 8A indicates, the supporting device in accordance with the invention has in the area of the folded-over gasket layer section 80 a or the folded-over gasket layer sections 80 a an effective height which is equal to the difference between the material thicknesses of the gasket layers 80 and 82.

In the area of this embodiment shown in FIG. 8B, the thicker gasket layer 80 has a folded-over gasket layer section 80 b which is folded over onto the thinner gasket layer 82 so that the supporting device in accordance with the invention has an effective height there which is equal to the material thickness of the gasket layer 80. The folded-over gasket layer section 80 b (or several such gasket layer sections) could lie between two folded-over gasket layer sections 80 a, but the thinner gasket layer 82 must then engage in the area of a folded-over gasket layer section 80 b under the latter. In this case, a supporting device in accordance with the invention has a height profile with two different effective heights, formed by folded-over gasket layer sections 80 a and 80 b, although only sections of a single gasket layer, namely the gasket layer 80, were folded over. Alternatively, the gasket plate could have a supporting device in accordance with the invention, formed by one or more folded-over gasket layer sections 80 a of the gasket layer 80 and one or more folded-over gasket layer sections of the thinner gasket layer 82.

FIG. 8C shows a variant of the area shown in FIG. 8A of a flat gasket in accordance with the invention, this area also having a thicker gasket layer 80 and a thinner gasket layer 82. Again the thicker gasket layer 80 is provided with at least one folded-over gasket layer section 80 a′, which is folded back onto the actual gasket layer 80, but, in this modification, engages in a cutout 82 a′ in the thinner gasket layer 82 and is substantially accommodated by this cutout, apart from the fact that the folded-over gasket layer section 80 a projects above the gasket layer 82 in the direction perpendicular to the gasket plate, more specifically, by the difference between the material thicknesses of the gasket layers 80 and 82. Apart from the cutout or the cutouts 82 a′, in the modification shown in FIG. 8C, the edge of the thinner gasket layer 82 runs in the immediate vicinity of the bending line resulting from formation of the folded-over gasket layer section or the folded-over gasket layer sections 80 a′. In other respects, the same applies for the modification shown in FIG. 8C as for the embodiments shown in FIGS. 8A and 8B.

FIG. 9 shows a modification of the flange connection, shown in FIG. 5, containing a flat gasket in accordance with the invention, with two flanges 30′ and 40′. In comparison with FIG. 5, the flange connection in FIG. 9 has been completed to the right as far as a right, in accordance with FIG. 9, edge of the flange connection. A gasket plate 100, shown only partially in FIG. 9, of a flat gasket in accordance with the invention has a thicker gasket layer 90 and a thinner gasket layer 92, however, it could also comprise further gasket layers. Just as in the embodiment shown in FIG. 5, the gasket plate 100 drawn in FIG. 9 has several folded-over gasket layer sections, more specifically, gasket layer sections 92 a of the thinner gasket layer 92 and gasket layer sections 90 a of the thicker gasket layer 90, which have all been folded over onto the thinner gasket layer 92. In the embodiment in accordance with FIG. 9, assembly screws 102 serve to connect the two flanges 30′ and 40′ to each other and to clamp the flat gasket between these two flanges. Each of the assembly screws 102 passes through a smooth screw hole 30 a′ of the flange 30′ and is screwed into a threaded bore 40 a′ of the flange 40′, and each assembly screw 102 has a screw head 104 which is tightened against the flange 30′.

In accordance with the invention, the following further modifications are possible and under certain circumstances advantageous: In the embodiment shown, the thicker gasket layer 90 has a screw hole 90′ for each assembly screw 102, while the thinner gasket layer 92 terminates before the shaft of each assembly screw 102 (seen from the gasket layer 92 to the outer edge of the flange connection). It is, however, also possible to also allow the thicker gasket layer 90 to terminate before the shaft of each assembly screw 102. Such modifications of the gasket plate of the flat gasket in accordance with the invention may result in slight deformations of the shafts of the assembly screws, but, on the other hand, the advantage is achieved that the effective heights of supporting devices in accordance with the invention are further graduated—in comparison with embodiments in which the height profiles of supporting devices in accordance with the invention are only determined by folded-over gasket layer sections. These modifications also allow the distribution of the pressing forces applied by the assembly screws 102 to be additionally influenced by the sealing gap accommodating the flat gasket. Merely for the sake of completeness, it is also pointed out that the illustration of the deformations of the flanges and the topography of the sealing gap is also exaggerated in FIG. 9 in order to show both clearly.

As is clear from the above description, the appended drawings and the attached claims, a basic concept of the invention is to be seen in that a flat gasket in accordance with the invention comprises at least two gasket layers having material thicknesses which differ from each other, and folded-over gasket layer sections are provided on at least one of these layers, more specifically, preferably on the gasket layer having the greater material thickness. Alternatively, the folded-over gasket layer sections could, however, also be provided on the gasket layer having the lesser material thickness, and at least one of these gasket layer sections is then folded over several times.

In preferred embodiments of the flat gasket in accordance with the invention, comprising at least two gasket layers, one of which has a larger layer thickness than the other, the layer thickness of the thicker gasket layer is from 1.2 to 1.6 times the layer thickness of the thinner gasket layer, in particular, from 1.25 to 1.5 times the layer thickness of the thinner gasket layer.

The difference between the layer thicknesses is preferably from approximately 0.05 to 0.1 mm.

Particularly recommendable is an inventive configuration in the case of multilayered flat gaskets having at least two gasket layers of different layer thickness, in which the layer thickness of the thinner gasket layer is from approximately 0.18 to 0.22 mm and, in particular, approximately 0.2 mm, and the layer thickness of the thicker gasket layer is from approximately 0.22 to 0.32 mm and, in particular, from 0.25 to 0.30 mm.

When mention is made hereinabove of two gasket layers arranged on each other or on top of each other, this is not to be understood as meaning that the two gasket layers must be immediately adjacent to each other, although such embodiments are preferred. It is possible for another gasket element such as a further gasket layer to also be arranged between the two gasket layers in question. 

1. A flat gasket comprising an at least substantially metallic gasket plate, which has at least two gasket layers arranged on each other and in which at least one through-opening to be sealed is formed, the gasket plate comprising at least one supporting device which increases the total material thickness of the gasket plate in areas thereof and is formed by several folded-over gasket layer sections, the gasket plate having at least one first gasket layer with at least one first layer area in which the first gasket layer has a first layer thickness and in which at least one first folded-over gasket layer section of a supporting device is formed, and the gasket plate having at least one second gasket layer with at least one second layer area in which the second gasket layer has a second layer thickness and in which at least one second folded-over gasket layer section of this supporting device is formed, the first and second layer thicknesses being different from each other and this supporting device, therefore, having different total material thicknesses in areas thereof
 2. The flat gasket in accordance with claim 1, wherein at least one gasket layer comprises a sealing bead which—in a plan view of the gasket plate—has a supporting device configured as stopper for the bead associated with and adjacent to it.
 3. The flat gasket in accordance with claim 1, wherein the at least one gasket layer comprises a sealing bead enclosing a fluid through-opening, and the supporting device is arranged—in relation to the through-opening—radially outside of the sealing bead.
 4. The flat gasket in accordance with claim 1, wherein at least one supporting device is provided at the periphery of the gasket plate.
 5. The flat gasket in accordance with claim 1, wherein the layer thickness of the first gasket layer is different from the layer thickness of the second gasket layer.
 6. The flat gasket in accordance with claim 5, wherein the first and second gasket layers comprise sheet metal layers of sheet metals of different sheet thickness.
 7. The flat gasket in accordance with claim 1, wherein at least when the flat gasket is installed, the folded-over gasket layer sections of a supporting device all lie on a first main surface of a gasket layer.
 8. The flat gasket in accordance with claim 7, wherein the first main surface forms a first outer side of the multilayered gasket plate.
 9. The flat gasket in accordance with claim 8, wherein at least one folded-over gasket layer section is formed by a gasket layer which forms the second outer side of the gasket plate and engages over the first outer side thereof.
 10. The flat gasket in accordance with claim 1, wherein at least some of the gasket layer sections are of tongue-shaped configuration and are folded over around the respective tongue root.
 11. The flat gasket in accordance with claim 1, wherein at least some of the gasket layer sections are of strip-shaped configuration and are folded over at a longitudinal edge of the respective gasket layer section.
 12. The flat gasket in accordance with claim 1, wherein at least one supporting device—in a plan view of the gasket plate—is of elongate configuration and is formed by at least two folded-over gasket layer sections lying one behind the other in the longitudinal direction of the supporting device, the total material thicknesses of the gasket plate in the areas of at least two gasket layer sections being different from each other.
 13. The flat gasket in accordance with claim 12, wherein the layer thicknesses of at least two gasket layer sections are different from each other.
 14. The flat gasket in accordance with claim 12, wherein the supporting device is formed by at least two first folded-over gasket layer sections provided in the longitudinal end areas of the supporting device and at least one second folded-over gasket layer section provided in a central area of the supporting device, the total material thicknesses of the gasket plate in the areas of the first gasket layer sections and in the area of the second gasket layer section being different from one another.
 15. The flat gasket in accordance with claim 14, wherein—in a plan view of the gasket plate—the elongate supporting device extends between two screw holes for the passage of assembly screws, and the total material thickness of the supporting device in areas near the screw holes is less than in a central area of the supporting device lying between these areas near the screw holes.
 16. The flat gasket in accordance with claim 1, wherein the gasket plate comprises at least one thicker and one thinner gasket layer, and the supporting device comprises at least two gasket layer sections of the thicker gasket layer, a first one of which is folded over onto the thicker gasket layer and a second one of which is folded over onto the thinner gasket layer.
 17. The flat gasket in accordance with claim 16, wherein the thinner gasket layer has a recess which—in a plan view of the gasket plate—accommodates the folded-over first gasket layer section at least substantially, and the total material thickness formed by the thicker and thinner gasket layers in the area of the folded-over second gasket layer section is, therefore, greater by the layer thickness of the thinner gasket layer than in the area of the folded-over first gasket layer section.
 18. The flat gasket in accordance with claim 1, wherein the two gasket layers extend at least substantially over the entire gasket plate.
 19. A flat gasket comprising an at least substantially metallic gasket plate, which has at least two gasket layers arranged on each other and in which at least one through-opening to be sealed is formed, the gasket plate comprising at least one supporting device which increases the total material thickness of the gasket plate in areas thereof and is formed by several folded-over gasket layer sections, the gasket plate having at least one first gasket layer with a first layer thickness and a second gasket layer with a second layer thickness, the first layer thickness being greater than the second layer thickness, and the supporting device comprising at least one first and one second folded-over gasket layer section of the first gasket layer, the first gasket layer section being folded over onto the first gasket layer, and the second gasket layer section being folded over onto the second gasket layer.
 20. The flat gasket in accordance with claim 19, wherein the second gasket layer has a recess which—in a plan view of the gasket plate—accommodates the folded-over first gasket layer section at least substantially, and the total material thickness formed by the first and second gasket layers in the area of the folded-over second gasket layer section is, therefore, greater by the second layer thickness than in the area of the folded-over first gasket layer section. 